I've not found anything to work like Google Adsense. For me, that's the best. I've tried banner ads from commission junction, but I never made a dime.
The most lucrative would be pay per lead/sale. This does not mean pay per click isn't profitable, but the people that make the a lot of money usually prefer pay per lead/sale because of the high payout rates.
Pay per lead. Sign up with an affiliate network. EliteCommission.com is a good affiliate network. They have high payouts! Have fun!
You should try pay per lead or sale if you have a skill for optimization of your traffic sources. Else, i suggest you try either per click or per impression using adsense and other tools For a good affiliate program, try the neverblue ads link in my signature
CJ works well but you need to have links to sites that are relevant for your visitors. If you have an automobile site stick with automotive based links. The highest paying affiliate programs are the ones that acquire the highest conversions. If your looking for an affiliate program that has a little of everything check out my second signature.
Pay per conversion are the best, but some merchant are dishonest and refuse to pay . I lost $125 once
To understand what is most profitable, you need to understand how things work. Merchants can pay based on the profit they make. Profit is derived from sales. Sales are derived from leads. Leads are derived from clicks. Clicks are derived from impressions. What is most profitable to you depends on the type of traffic you have. If your traffic leads to high numbers of conversions to leads/sales then you can make the most money with pay-per-sale (assuming the merchant can track your conversions separately from the rest of affiliates). If you have a lot of traffic but despite clicking on ads, your visitors do not buy as well as people from other sources, you will make more money from clicks since the merchants use average clicks-to-sales ratios to decide how much to pay for each click. If yours is below-average, you will make more money by getting "average" pay-per-click rate. If your clicks-to-sales ratio is high you will lose money by getting "average" per-per-click rate since your rate is diluted by others not as good traffic.